Operation Epsilon: When Allied Forces Locked Ten German Scientists Together in a House

Feb 1, 2022 0 comments

Near the end of World War 2, the Allied forces arrested ten German scientists who were thought to have worked on Nazi Germany's nuclear program and housed them together at a bugged country house called Farm Hall in Godmanchester, near Cambridge, England. For six months from July 1945 to January 1946, a team of operators listened to and recorded their conversation in the hope that the scientists would divulge information that would help the Allied determine whether Germany had worked out the intricate details needed for making a working nuclear bomb, and if not, how close they got into making one. The operation was nicknamed Epsilon.

Farm Hall,

Farm Hall, where the ten German scientists were incarcerated.

The ten scientists who were under observation were Erich Bagge (developed a method to enrich uranium, an essential step to making a nuclear device); Kurt Diebner (the administrative director of the Nazi German nuclear weapons program); Walther Gerlach (co-discovered, along with Otto Stern, the spin quantization in a magnetic field, the Stern–Gerlach effect); Otto Hahn (discovered nuclear fission, for which he was awarded the Nobel Prize in chemistry); Paul Harteck (worked on uranium isotope separation), Werner Heisenberg (known for the uncertainty principle, he was the principal scientist in the German nuclear weapons program); Horst Korsching (worked on isotope separation); Max von Laue (discovered the diffraction of X-rays by crystals); Carl Friedrich von Weizsäcker (was one of the first scientist who recognized that nuclear weapons could be built soon after Otto Hahn made public his theory of nuclear fission); and Karl Wirtz (worked on nuclear reactor design).

Operation Epsilon

Top row (L to R): Werner Heisenberg, Paul Harteck, Max von Laue, Otto Hahn
Middle row (L to R): Erich Bagge, Carl Friedrich von Weizsäcker, Walther Gerlach, Horst Korsching
Third row (L to R): Kurt Diebner, Karl Wirtz

Shortly after they were rounded up and interned at Farm Hall, Kurt Diebner expressed concern that the house might have hidden microphones installed for listening, an idea which Heisenberg naively dismissed. “Microphone installed?”, he asked rhetorically, “Oh no, they're not as cute as all that. I don't think they know the real Gestapo methods; they're a bit old fashioned in that respect.”

The most fascinating thing about these conversations is the insight they give into the minds of ten individuals, each weighing for himself a variety of competing loyalties, to humanity, to science, to his country and duty, to his group, to his family and to his career.

The greater part of these conversation revolved around determining how much fissile material was needed before it can possibly undergo a nuclear explosion—a value known as the critical mass. None of the scientists had the vaguest idea what the critical mass is for uranium-235; their guesses ranged from a few kilograms to several tons. Heisenberg’s own estimate for the critical mass was all over the place. On 6 August 1945 he was heard saying much more than 50 kg, but he was prepared to accept values as large as 500 or even 5000 kg. He then admited to Otto Hahn that he never worked it out properly. A week later, having tackled the problem a bit more seriously, he arrived at a critical mass lying between 20 kg and 210 kg.

It was clear that Heisenberg's miscalculation of the critical mass for a nuclear explosion was of crucial importance for determining German nuclear energy policy during the war. Heisenberg was of the opinion that a nuclear bomb could not be made during the duration of the war, and that conclusion was received with welcome relief. Heisenberg may well have thought that it was not worth spending effort on an accurate calculation before he had better knowledge of the nuclear parameters. Heisenberg, as well as the rest, were probably greatly relieved by the conclusion that there would be no bomb within the duration of the war, thus absolving them from very difficult decisions.

Farm Hall,

Farm Hall in Godmanchester, England.

In the evening of August 6, when news of the first atomic bomb was relayed to the incarcerated scientists, they were completely staggered. At first they refused to believe it and felt the Americans were bluffing.

”All I can suggest is that some dilettante in America who knows very little about it has bluffed them in saying "If you drop this it has the equivalent of 20,000 tons of high explosive" and in reality doesn't work at all,” said Heisenberg.

“I am willing to believe that it is a high pressure bomb and I don't believe that it has anything to do with uranium but that it is a chemical thing where they have enormously increased the speed of the reaction and enormously increased the whole explosion,” Heisenberg added.

When they heard the official announcement at nine o’clock, they still could not believe their ears. Otto Hahn was completely shattered for he felt personally responsible for the deaths of hundreds of thousands of people, as it was his original discovery (nuclear fission) which had made the bomb possible.

“I didn't think it would be possible for another twenty years,” Otto Hahn admitted.

He turned to Heisenberg and said, “You're just second-raters and you may as well pack up,” to which Heisenberg agreed.

“They are fifty years further advanced than we,” Hahn remarked.

“I'm glad we didn't have it,” reckoned Karl Wirtz.

“I think it's dreadful of the Americans to have done it. I think it is madness on their part,” Carl Friedrich von Weizsäcker weighed in.

“One can't say that,” Heisenberg countered. “One could equally well say "That's the quickest way of ending the war.”

The discussion then turned to why Germany was not able to accomplish what the Americans and the British had. Horst Korsching commented on the immense cooperation a project of such scale required. “That would have been impossible in Germany,” he said. “Each one said that the other was unimportant.”

WEIZSACKER: How many people were working on V l and V 2?

DIEBNER: Thousands worked on that.

HEISENBERG: We wouldn't have had the moral courage to recommend to the Government in the spring of 1942 that they should employ 120,000 men just for building the thing up.

WEIZSACKER: I believe the reason we didn't do it was because all the physicists didn't want to do it, on principle. If we had all wanted Germany to win the war we would have succeeded.

HAHN: I don't believe that but I am thankful we didn't succeed

HEISENBERG: It is possible that the war will be over tomorrow.

HARTECK: The following day we will go home.

KORSCHING: We will never go home again.

HARTECK: If we had worked on an even larger scale we would have been killed by the "Secret Service". Let's be glad that we are still alive. Let us celebrate this evening in that spirit.

HEISENBERG: The point is that the whole structure of the relationship between the scientist and the state in Germany was such that although we were not 100% anxious to do it, on the other hand we were so little trusted by the state that even if we had wanted to do it it would not have been easy to get it through.

DIEBNER: Because the official people were only interested in immediate results. They didn't want to work on a long-term policy as America did.

WEIZSACKER: Even if we had got everything that we wanted, it is by no means certain whether we would have got as far as the Americans and the English have now. It is not a question that we were very nearly as far as they were but it is a fact that we were all convinced that the thing could not be completed during this war.

Heisenberg expressed irritation that he couldn’t work out how the Americans had managed to build the bomb. “I find it is a disgrace if we, the Professors who have worked on it, cannot at least work out how they did it,” he growled.

”These fellows have succeeded in separating isotopes. What is there left for us to do?,” Wirtz asked.

“What depresses me is the thought that all the work we may do in Germany will, so to speak, fall into the laps of other people,” Korsching lamented.

The scientists also discussed the scenario where Germany had invented the bomb first.

WIRTZ: The result would have been that we would have obliterated London but would still not have conquered the world, and then they would have dropped them on us.

WEIZSACKER: I don 't think we ought to make excuses now because we did not succeed, but we must admit that we didn't want to succeed. If we had put the same energy into it as the Americans and had wanted it as they did, it is quite certain that we would not have succeeded as they would have smashed up the factories.

WEIZSACKER: One can say it might have been a much greater tragedy for the world if Germany had had the uranium bomb. Just imagine, if we had destroyed London with uranium bombs it would not have ended the war, and when the war did end, it is still doubtful whether it would have been a good thing.

The scientists also expressed concern about their families and where they might land up after they are released, and whether they would be allowed to return to Germany. Some expressed desire to work for the British or the Americans, and settle in Britain. “I would have no pangs of conscience in making neutron sources for the Americans,” said Korching

All ten scientists were released from detention on January 3, 1946, after which they were allowed to return to Germany.

Paul Harteck left for Hamburg where he became director of the chemistry department at the University, a position he held until 1950. Harteck them moved to America and became a resident professor at the Rensselaer Polytechnic Institute in Troy, New York. He was nominated for the Nobel Prize in Chemistry twice, first before the war in 1937 and the second time in 1952.

Kurt Diebner set up a private Institute for Measuring Instruments in Hamburg, and later became a member of the supervisory board company that oversees exploitation of nuclear energy in ship building and shipping.

After his incarceration, Korsching worked at the Max-Planck Institut für Physik (MPIP).

Gerlach returned to Germany and became a visiting professor at the University of Bonn. A year later, he became a professor of experimental physics and director of the physics department at the University of Munich, of which he was also the rector.

Max von Laue went back to being acting director of the Kaiser-Wilhelm Institut für Physik (KWIP) which became the Max-Planck Institut für Physik. Laue also became an adjunct professor at the University of Göttingen.

Bagge became Professor in Hamburg, later Professor and Head of the Department of Physics at the University of Kiel, Germany. He was also Head of the Gesellschaft für Kernenergieverwertung in Schiffbau und Schiffahrt (GKSS) near Hamburg.

Weizsäcker became director of a department for theoretical physics in the Max Planck Institute for Physics in Göttingen. Later, he became head of the Max Planck Institute for the Research of Living Conditions in the Modern World in Starnberg. He researched and published on the danger of nuclear war, what he saw as the conflict between the First World and the Third World, and the consequences of environmental degradation.

Karl Wirtz worked at the Max-Planck Institut für Physik, and then he became a professor at the University of Göttingen.

After his return to Germany, Heisenberg became the director of the Max Planck Institute for Physics. Heisenberg together with Hermann Rein was instrumental in the establishment of the Forschungsrat, a research council whose goal was to promote the dialogue between the newly founded Federal Republic of Germany and the scientific community based in Germany.

Otto Hahn took over the presidency of the Kaiser-Wilhelm-Gesellschaft from the ailing Max Plank. Hahn also secured Max Planck's agreement to lending his name to the Society, which then became Max Planck Society. After the war, he became a vocal opposer to the use of nuclear energy for military purposes. He saw the application of his scientific discoveries to such ends as a misuse, or even a crime.

# Charles Frank, Operation Epsilon: The Farm Hall Transcripts


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